• Energetic cost functions of speed were acquired for red kangaroos, echidnas and humans from the literature (2, 3, 4, 5, 6, 7)

• Functions transformed into comparable units and averaged• VO2 measurements were used as a metric for energy consumption• Measurements were taken well below VO2max (80% heart rate of

VO2max) so that anaerobic respiration has little effect (5)• All functions are in per-kilogram units to allow for direct comparison • Functions were plotted for visual comparison (Figure 1)

Results• Kangaroo efficiency decreases drastically with speed• Human efficiency becomes somewhat constant with speed• Both human and kangaroo are very inefficient runners at low speeds• The oldest cross country ski is similar in efficiency to human running• Newer skis are comparable in efficiency to walking• Intercepts between ski and kangaroo functions indicates the speed

beyond which the kangaroo is more efficient

• The ski has evolved, becoming more efficient with technological advances

• Improved efficiency in human locomotion rivals that of a human walk and kangaroo run

• Kangaroos, on average travel 6 m/s (3) while running suggesting that the ski was similar to the kangaroo in efficiency around 1300 CE

Caveats of Generalized Functions• Generalized functions do not account for other types of

gaits that humans and kangaroos employ• Functions don’t consider anaerobic respiration which

occurs at high speeds (6, 5)• Measurements were taken on a treadmill which negates

air resistance• An echidna cannot run 20 m/s

• Compare locomotion costs among mammals

• Compare the efficiency of skier locomotion to kangaroo locomotion

• Assess the ski as an evolutionary adaptation

• Since the first mobile organism crawled onto the earth (443.4-419.2 Mya) (1) a ‘race’ for the most efficient terrestrial locomotion has taken place.

• Tendons have evolve to recycle kinetic energy that would otherwise be lost.

• Kangaroo legs (Achilles tendon) have become so efficient that efficiency increases with speed (2, 3)

• The ski has evolved over the last 5000 years (4) as a tool not only to travel on deep snow but also to improve the efficiency of travel on hard snow

• The ski has become so efficient that it surpasses regular human locomotion (running)

• Skiing thus became one of the most efficient modes of terrestrial locomotion across a range of speeds in the animal kingdom

Introduction Methods

Objectives

Discussion

Conclusion• Human inventiveness has resulted in an evolved

locomotion that not only betters its own efficiency, but becomes comparable to one of the most efficient runners in the animal kingdom.

References1. Engel, M. S., & Grimaldi, D. A. (2004). New light shed on the oldest insect.Nature, 427, 627-630.2. Dawson, T. J., & Taylor, C. R. (1973). Energetic cost of locomotion in kangaroos.3. Kram, R., & Dawson, T. J. (1998). Energetics and biomechanics of locomotion by red kangaroos (Macropus rufus). Comparative

Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 120, 41-49.4. Formenti, F., Ardigò, L. P., & Minetti, A. E. (2005). Human locomotion on snow: determinants of economy and speed of skiing

across the ages.Proceedings of the Royal Society B: Biological Sciences, 272, 1561-1569.5. Margaria, R., Cerretelli, P., Aghemo, P., & Sassi, G. (1963). Energy cost of running. Journal of Applied Physiology, 18, 367-370.6. Cavagna, G. A., & Kaneko, M. (1977). Mechanical work and efficiency in level walking and running. The Journal of

Physiology, 268, 467-481.7. Crompton, A. W., Taylor, C. R., & Jagger, J. A. (1978). Evolution of homeothermy in mammals. Nature, 272, 333-336.8. Taylor, C. R., Heglund, N. C., & Maloiy, G. M. (1982). Energetics and mechanics of terrestrial locomotion. I. Metabolic energy

consumption as a function of speed and body size in birds and mammals. Journal of Experimental Biology, 97, 1-21.Image Creditshttp://www.eplantscience.com/index/general_zoology/muscle_performance.phphttp://progress-is-fine.blogspot.ca/2014/02/cross-country-skiing.htmlKnud Bergslein http://mediumaevum.tumblr.com/post/15466427268/the-primitive-ski-dated-back-to-1010Sergey Vasilyevich Ivanov (1884-1910) from http://en.wikipedia.org/wiki/File:Pokhodmoskovityan.jpghttps://yhsbiology.wikispaces.com/Kangaroos+and+Opossumshttp://theoallofs.photoshelter.com/image/I0000fW4zuTqIxjE

Being Kangaroo: The Quest for Efficient LocomotionBen Millard-Martin, BIOL 325, Biology Program, UNBC

Ben Millard-Martin: millard@unbc.ca

Figure 1: Plotted functions of work per unit distance dependant upon speed of historical skis, human echidna and kangaroo.

Walk